1. Field of the Invention
The present invention relates to a scroll compressor, and more particularly, to a vacuum preventing device for a scroll compressor in which gas in a discharge region flows backward to a suction region at the time of an abnormal driving such as when pump is down or when an expansion valve is blocked, thereby preventing a vacuum of the compressor.
2. Description of the Background Art
Generally, a compressor is a device for converting mechanical energy into latent energy of a compression fluid. Generally they can be classified as a reciprocation compressor, a scroll compressor, a centrifugal compressor, and a vane compressor based upon the compression method.
The scroll compressor has a structure such that gas is taken-in, compressed, and discharged by using a rotation member, such as the centrifugal type and the vane type, differently from the reciprocating type which uses a linear reciprocation of an open/close member.
FIG. 1 is a longitudinal sectional view showing an inner part of the conventional scroll compressor.
As shown, the scroll compressor comprises: a case 1 divided into a gas suction tube SP and a gas discharge tube DP; a main frame 2 and a sub frame (not shown) respectively installed at both upper and lower portions of an inner circumference surface of the case 1; a driving motor 3 installed between the main frame 2 and the sub frame; a rotation shaft 4 engaged with a center portion of the driving motor 3 for transmitting a rotation force of the driving motor 3; an orbiting scroll 5 installed to have an eccentric rotation at an upper portion of the rotation shaft 4 and having a wrap 5a of an involute curve shape at the upper portion thereof; and a fixed scroll 6 fixed to an upper portion of the main frame 2, engaged to the orbiting scroll 5, and having a wrap 6a of an involute curve shape so as to form a plurality of compression spaces P therein.
The case 1 is divided into a suction region S1 and a discharge region S2 by a high and low pressure separation plate 7, and a compression region S3 is formed at a position connected to the compression space P.
A gas inlet 6b and an outlet 6c are respectively formed at a lateral surface and a center portion of the fixed scroll 6, and a non-return valve 8 for preventing discharged gas from flowing backward is installed at an upper surface of the fixed scroll 6.
The main frame 2 and the sub frame are fixed to the inner circumference surface of the case 1 by a fixation means such as welding, and the fixed scroll 6 is also fixed to a bottom surface of the high and low pressure separation plate 7 by a fixation means such as a bolt.
Meantime, in case that a pump is down and an expansion valve blockage, the suction region S1 of the compressor becomes a high vacuum state. As a result, components of the compressor may be damaged and destroyed.
To prevent this problem, a vacuum preventing device 20 is provided in the conventional art.
FIG. 2 is a longitudinal sectional view showing an operation during normal driving, of the vacuum preventing device of FIG. 1, and FIG. 3 is a longitudinal sectional view showing an operation during abnormal driving of the vacuum preventing device of FIG. 1.
Referring to FIGS. 2 and 3, the vacuum preventing device 20 includes a chamber 10 formed at one side of the fixed scroll 6, and a discharge hole 11 connected to the discharge region S2 at an upper surface of the chamber 10.
A compression hole 12 connected to the compression region S3 is formed at a bottom surface of the chamber 10, a plug 14 having a suction hole 13 is fixed to an opening portion of the chamber 10 by a fixation pin 15, and the suction hole 13 is connected to the discharge hole 11.
An open/close member 17 for selectively connecting the discharge hole 11 and the suction hole 13 is movably installed in the chamber 10.
A spring 16 for limiting a movement of the open/close member 17 and providing an elasticity force thereto is installed at the opening portion of the chamber 10.
Hereinafter, operations of the conventional scroll compressor will be explained.
First, when a power source is applied to the driving motor 3, the driving motor 3 rotates the rotation shaft 4, and the orbiting scroll 5 engaged to the rotation shaft 4 is rotated to an extent of its eccentric distance.
At this time, a plurality of compression spaces P formed between the wrap 5a of the orbiting scroll 5 and the wrap 6a of the fixed scroll 6 gradually move towards a center portion of the fixed scroll 6 as the orbiting scroll 5 continuously performs an orbiting movement, thereby causing a decreased volume.
By the decreased volume of the compression spaces P, gas of the suction region S2 is taken into the compression space P through the inlet 6b, and the taken gas is discharged to the discharge region S2 through the outlet 6c. 
When the compressor is normally driven (FIG. 2), a pressure of the compression region is larger than an elasticity force of the spring 16, so that the open/close member 17 overcomes the elasticity force of the spring 16 and shields (i.e., abstracts) the discharge hole 11.
However, when the compressor is abnormally driven (FIG. 3), a pressure of the compression region is smaller than the elasticity force of the spring 16, so that the open/close member 17 is moved by the elasticity force of the spring 16 and opens the discharge hole 11. At this time, the discharge hole 11 is connected to the suction hole 13.
As the discharge hole 11 and the suction hole 13 are connected to each other, gas of the discharge region S2 flows backward into the suction region S1 through the discharge hole 11 and the suction hole 13, thereby releasing a vacuum of the compressor.
Moreover, in the conventional art, since the vacuum preventing device is formed in the fixed scroll, a fabrication cost is expensive and a strength of the fixed scroll is degraded, thereby easily destroying the fixed scroll at the time of an operation.